Shellexview did the trick. Had to disable and reboot several times until I found it was old Western Digital External hard drive extensions. The hard drive still works fine in Windows 10 1903, but...

1903 Update, Now File Explorer takes 30-60 seconds to open. Once opened, right-clicking files takes 30-60 seconds to respond with the appropriate pop-up. Selecting properties on the ribbon bar...

This issue started for me after the 1903 update! Takes about 30 seconds to first open file explorer, or right-click items. I can cut and paste fine using the icons in the ribbon, but right-clicking...